Abstract: Objective To analyze the cost-benefit of the project for syphilis prevention of mother-to-child transmission in Shenzhen and provide scientifice evidence for government policy making.Method Using the cost-benefit theory of socio-economic to investigate the result of antenatal syphilis screening,the staff of the project and the clinical specialists were interviewed,follow ing-up was made to families with syphilis to find out the cost paid by the health care provider and patients and the intangible cost of the patients in the project.Result The total cost of the project was' 27 627 552.36,which included the direct cost' 1 138 451.79(41.2%),the indirect cost' 20 448 850.57(74.02%),intangible cost' 6 040 250.00(21.86%).In other words it included agency cost(73.84%),the family cost(26.16%),the medical cost(3.56%) and the social cost(96.44%).The total benefit was' 134 898 188.07,which included the direct benefit' 2 608 080.26,the indirect benefit' 127 412 357.81,and the intangible benefit' 4 877 750.00 as well.The benefit-cost ratio of the project in 2003 was 4.88:1,among which the direct benefit cost ratio(BCR)2.29:1,the indirect BCR was 6.23:1,the intangible BCR 0.81:1.Conclusion Antenatal syphilis screening is a lower-input and higher-output public welfare project,not only in economic but also in society.